Analysis of Water Body Segmentation from Landsat Imagery using Deep Neural Network

Wireless Personal Communications - The water body segmentation is precious for assessing its role in ecosystem services with the circumstances of climate change and global warming. The accurate...     

Investigation of natural convection via heatlines for Rayleigh–Bénard heating in porous enclosures with a curved top and bottom walls

The current study deals with the heatline-based analysis of natural convection in porous cavities with the curved top and bottom walls involving the Rayleigh–Bénard heating. The streamline cells are weak, and the wall-to-wall heatlines are observed for all the cases at the low Da_m involving two test cases, Pr_m?=?0.015 and 7.2. At the high Da_m, the convective force takes the command, and multiple heatline cells are observed for all the concave (except for high wall concavity) and convex cases. The directions of the streamlines (for all Da_m) and heatlines (at the high Da_m) are exactly opposite for the concave and convex cases. The case 3 (concave) is the efficient case based on the largest heat transfer rate for Pr_m?=?0.015 involving all Da_m and for Pr_m?=?7.2 involving the low Da_m. At Pr_m?=?7.2 and high Da_m, the case 1 (concave or convex) may be the efficient cases compared with the cases involving high wall curvatures.     

Structural, dielectric and conductivity studies of Na2Pb2La2W2Ti4Nb4O30 ferroelectric ceramic

A new single phase orthorhombic ferroelectric ceramic Na₂Pb₂La₂W₂Ti₄Nb₄O₃₀ (NPLWTN) was prepared via high-temperature solid-state reaction method. The grain morphology of the compound was analyzed by scanning electron microscopy (SEM). Studies of dielectric properties (??_r and tan??) of the compound at different frequencies (10²?C10⁶?Hz) in a wide temperature range (300?C700?K) showed multiple phase transitions in it. First phase transition observed at 335?K related to structural type (ferroelectric-ferroelectric) and the second one observed at 536?K is related to the ferroelectric to paraelectric. The ferroelectric property of the compound at room temperature was confirmed by polarization (hysteresis) study. Broadened dielectric peaks at low frequencies were observed above ferroelectric to paraelectric phase transition temperature (Tc). The values of exponent n(T) and pre-factor A(T) at and around Tc were obtained by the fitting ac conductivity data with Jonscher??s universal power law. From the variation of n(T) and A(T) with temperature, the strength of interaction among the charge carriers with the crystal lattice and the strength of polarisability at phase transition are observed. The activation energy of the compound in low and high temperature range suggests the conduction mechanism in the material.     

Minimum fluidization velocity at elevated temperature in tapered fluidized bed

Very little data of minimum fluidization velocity at elevated temperatures of tapered bed are available in the literature. This study was undertaken to provide some data under elevated temperature conditions in tapered bed. Data on minimum fluidization velocity have been obtained experimentally for temperature up to 800 °C in case of 0.5 mm diameter of sand particles and up to 500 °C in case of 1 mm diameter of glass beads in tapered bed. An equation valid for the bed has been developed in terms of Archimedes number and Reynolds number. The experimental values for minimum fluidization velocity at elevated temperatures have been compared with the calculated values obtained from present equation and from earlier equations developed by other authors for ambient conditions in conventional (cylindrical) bed and tapered bed. Fairly good agreement was found to exist between the calculated (from present equation) and the experimental values.     

Microwave-assisted preparation of poly(2-EHA-co-ST) copolymer and poly(2-EHA-co-ST)/MMT nanocomposite

Copolymerization of 2-ethylhexylacrylate and styrene was performed in presence of benzoyl peroxide as initiator at varying concentrations of the comonomers in a microwave oven. Montmorillonite (MMT) clay was added with a view to prepare nanocomposites, which actually enhanced the water absorption capacity and pressure sensitive adhesive properties. The copolymer and its nanocomposite were characterized by Fourier Transform Infrared, ¹H- and ¹³C-NMR, thermogravimetric-differential thermal analysis (TG-DTA), differential scanning calorimeter, scanning electron microscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The MMT layers were partially exfoliated/intercalated during the polymerization process as evident from the XRD and TEM observations. Their adhesive properties, water absorbancy, and biodegradability in different conditions were studied for their future applications. The monomer reactivity ratios were determined using Finemann–Ross and Kelen–Tüdos method. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Visible light response photocatalytic water splitting over CdS-pillared zirconium–titanium phosphate (ZTP)

With an attempt to extend the light absorption towards the visible range and inhibit the rapid recombination of excited electrons/holes, a new type photocatalysts, cadmium sulfide intercalated zirconium–titanium phosphate (CdS–ZTP) was synthesized. The photocatalysts were characterized by small angle X-ray diffraction studies (SAXS), N₂ adsorption–desorption studies, diffused reflectance UV–vis (DRUV–vis) spectroscopic analysis, photoluminescence studies (PL), scanning electron microscopic/energy dispersive spectroscopic (SEM/EDS), X-ray photoelectron spectroscopic (XPS) studies etc. The samples exhibit a unique property of optical absorption in UV and visible regions with a wavelength, λ ≤ 450 nm followed by a clear long tail up to 700 nm. The pillared materials showed excellent activity for UV–visible light driven hydrogen production from photocatalytic splitting of water without using any co-catalyst. The photocatalytic activity of this cadmium sulfide pillared catalyst, as well as that of neat cadmium sulfide powder, was monitored for the visible light-induced evolution of hydrogen from water in the presence of hole scavenger, sulfide (S²⁻).     

Rhodium‐Catalyzed Enantioselective Conjugate Addition of Arylboronic Acids to Dihydronitronaphthalenes

A highly enantioselective (up to 91% ee) rhodium‐catalyzed asymmetric addition of arylboronic acids has been achieved leading to the challenging dihydro‐3‐nitronaphthalenes using one equivalent of phosphoramidite ligand to rhodium catalyst. A concise formal asymmetric synthesis of the dopamine D1 agonist, dihydrexidine was accomplished using the method.     

Structural and luminescent properties of Eu3+-doped GdSrAl3O7 nanophosphor

Eu³⁺-doped GdSrAl₃O₇ nanophosphor with promising luminescent properties has been synthesized by low-temperature solution combustion synthesis. The structural properties examined by X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy showed that pure tetragonal GdSrAl₃O₇: Eu³⁺ red nanophosphor having narrow size distribution in 50–55 nm range could be readily obtained at low temperature 550 °C. The photoluminescent excitation and emission spectra, life time, and concentration effect were studied in detail. Under excitation at 266 nm, Eu³⁺-doped GdSrAl₃O₇ nanophosphor revealed weak green emission and strong red emission attributed to ⁵D₁ → ⁷F_1–2 and ⁵D₀ → ⁷F_0–3 transitions of Eu³⁺ ion, respectively in the region of 525–700 nm. The red emission from ⁵D₀ → ⁷F₂ transition at 616 nm exhibits the highest intensity under the optimized concentration of 10 mol% after which the quenching mechanism became relevant. Quenching behavior of the europium in the GdSrAl₃O₇ host was explained by nonradiative cross-relaxation phenomenon. Moreover, Eu³⁺-doped GdSrAl₃O₇ nanophosphor can generate light from orange to deeper red by properly tuning the concentration of europium ions based on the energy transfer principle.     

Combustion Synthesis and Optical Properties of Eu3+-Doped BaGd2ZnO5 f–f Transition Nanophosphor for White LED

An Eu³⁺-doped BaGd_2(1?x)ZnO₅ nanophosphor has been synthesized by means of a single-step, urea-assisted, solution-combustion process. The structural, morphological, and optical properties of the nanophosphor were studied by x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The XRD results showed that the pure orthorhombic BaGd₂ZnO₅ structure with space group Pbnm was obtained at 900°C. The intense red luminescence at 628 nm on near-UV (396 nm) excitation is because of the hypersensitive ⁵D₀ → ⁷F₂ transition of luminescent activator Eu³⁺ ions, located at a site with no inversion symmetry in the BaGd₂ZnO₅ crystal lattice. The optimum doping concentration and decay time of Eu³⁺-doped BaGd_2(1?x)ZnO₅ nanophosphor were also determined. The emission could be effectively tuned from blue to the white and red regions by varying the concentration of europium ions. Decay curve analysis revealed that cross-relaxation is primarily responsible for the concentration quenching. High luminescent intensity, low-cost, easy synthesis, uniform shape, and controlled color tunability suggest use of BaGd₂ZnO₅:Eu³⁺ as an efficient red-emitting nanophosphor for near-UV-based LED solid-state lighting applications.